Browse Prior Art Database

Threshold Personalized PLA Device and Method of Fabrication

IP.com Disclosure Number: IPCOM000085249D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Johnson, WS: AUTHOR [+2]

Abstract

Programmed Logic Arrays (PLA) are custom logic parts which are expensive, because the design time of new part numbers is short. They consist largely of read-only memories which are personalized by altering a single mask level. 1's and 0's are represented by devices which either can or cannot be turned on.

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Threshold Personalized PLA Device and Method of Fabrication

Programmed Logic Arrays (PLA) are custom logic parts which are expensive, because the design time of new part numbers is short. They consist largely of read-only memories which are personalized by altering a single mask level. 1's and 0's are represented by devices which either can or cannot be turned on.

Wafers are stockpiled just prior to metallization. Personalization is achieved by raising the threshold voltage of selected devices above that which is normally applied to the gate. Threshold personalization is amenable to fully automated personalization requiring no mask fabrication.

The detailed method is as follows: A portion of the PLA array is shown in the figure. Operation is normal. When the word-line potential raises, a bit line which is shorted to ground indicates a 0 and a bit line which is open to ground (and thus remains at a high voltage) indicates a 1.

In this device every metal-oxide semiconductor field-effect transistor (MOSFET) has a thin-oxide gate 14 and every gate is connected to the appropriate metal word line 12. As stockpiled, all FET's are fabricated normally through gate oxidation, passivation and ion-implant threshold adjust. The devices have normal enhancement-mode threshold voltages ( 1.0 volt for a 5 volt system). The diffused regions 10 are the source-drains of MOSFETS.

These devices are all in the 0 state. To change a device to the 1 state boron ions, for example, are impl...